# MCQs: Normal Probability

Find the area under the standard normal curve between z=0 and z=3.

A. 0.4987

B. 0.9987

C. 0.4641

D. 0.0010

IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15. An individual's IQ score is found to be 110. Find the z-score corresponding to this value.

A. -1.33

B. 1.33

C. -0.67

D. 0.67

The lengths of pregnancies of humans are normally distributed with a mean of 268 days and a standard deviation of 15 days. A baby is premature if it is born three weeks early. What percentage of babies are born prematurely?

A. 9.21%

B. 8.08%

C. 6.81%

D. 10.31%

The distribution of cholesterol levels in teenage boys is approximately normal with and (Source: U.S. National Center for Health Statistics). Levels above 200 warrant attention. Find the probability that a teenage boy has a cholesterol level greater than 225.

A 0.0718

B 0.0012

C 0.0336

D 0.0606

An airline knows from experience that the distribution of the number of suitcases that get lost each week on a certain route is approximately normal with ? = 15.5 and Ï? = 3.6. What is the probability that during a given week the airline will lose less than 20 suitcases?

A 0.4040

B 0.3944

C 0.1056

D 0.8944

Assume that blood pressure readings are normally distributed with and A blood pressure reading of 145 or more may require medical attention. What percentage of people have a blood pressure reading greater than 145?

A. 99.91%

B. 6.06%

C. 0.09%

D. 11.09%

Assume that the salaries of elementary school teachers in the United States are normally distributed with a mean of $32,000 and a standard deviation of $3000. If a teacher is selected at random, find the probability that he or she makes more than $36,000.

A. 0.1056

B. 0.0918

C. 0.4040

D. 0.9082

IQ test scores are normally distributed with a mean of 100 and a standard deviation of 15. Find the x-score that corresponds to a z-score of -1.645.

A. 79.1

B. 91.0

C. 82.3

D. 75.3

For the standard normal curve, find the z-score that corresponds to the 90th percentile.

A. 0.28

B 1.52

C 1.28

D 2.81

Find the z-scores for which 90% of the distribution's area lies between -z and z.

A.(-0.99,0.99)

B.(-1.645,1.645)

C.(-2.33,2.33)

D.(-1.96,1,96)

https://brainmass.com/statistics/z-test/mcqs-normal-probability-359438

#### Solution Summary

The solution provides answers to multiple choice questions on normal probability. Relevant workings are also included.

Normal Probability

12. Find the area under the normal distribution curve to the right of z = -3.24. (Points : 1)

0.499

-0.499

0.999

0.001

13. Use a scatter plot to deternine the relationship between the x values and the y values.

(Points : 1)

No relationship

Nonlinear relationship

Positive linear relationship

Negative linear relationship

14. The average hourly wage of employees of a certain company is $9.83. Assume the variable is normally distributed. If the standard deviation is $4.58, find the probability that a randomly selected employee earns less than $5.43. (Points : 1)

0.313 = 31.3%

0.332 = 33.2%

0.168 = 16.8%

0.345 = 34.5%

15. Find the area under the normal distribution curve between z = -1.34 and z = 2.95. (Points : 1)

0.908

0.088

0.410

0.498

16. Find the equation of the regression line.

(Points : 1)

y = -1.2 + 2.4x

y = 1.2 + 2.4x

y = 2.4 + 1.2x

y = -2.4 + 1.2x

18. Determine whether a correlation coefficient of r = -0.405 is significant at the 5% level for a sample size of 22. (Points : 1)

r is not significant at 5%.

r is significant at 5%.

19. Find the area under the normal distribution curve between z = 1.52 and z = 2.43. (Points : 1)

0.929

0.436

0.493

0.057

6. Use the equation of the regression line to predict y when x = 20.

(Points : 1)

45.5

50

40

48.5

7. Find the area under the normal distribution curve to the right of z = -1.03. (Points : 1)

0.151

-0.349

0.349

0.849

9. Find the value for the correlation coefficient r.

(Points : 1)

-0.073

-0.094

-0.203

-0.149

10. A data set of size 19 has correlation coefficient of r = -0.432. Test the significance of r at the 5% level and at the 1% level. (Points : 1)

r is significant at 5% and at 1%.

r is significant at 5%, but not at 1%.

r is is not significant at 5% or at 1%.

Please see the attachment.

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